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measurement of instantaneous amperage spike?

pvdude

Solar Enthusiast
Joined
Feb 8, 2021
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Location
Florida
What kind of meter or sensor do I need to “see” an instantaneous amperage spike?
I would like to investigate the possibility of running the home heat pump.
goodman_compressor_amps2021.png
I added a “Hard Start kit” when the 21KW Diesel genset demonstrated difficulty starting the compressor.
Now the genset does not sag when starting the compressor, but I have no idea what the modified LRA value is, so want to measure it.
I have a Fluke 177, w/ i410 AC/DC Current Clamp, but I am not sure it is fast enough.

I have room to install a second 6848 HW+ Pro.
If I understand how the two inverters will operate when stacked, 24kw of 30 second overload might be possible, enough to get the compressor started. That would be excellent!
 
what you need depends on what you want to see.
The "most" accurate would be a precision shunt resistor and storage scope (and simple storage scopes are rather cheap!)
if you really want to catch the entire startup waveform then you will want a storage scope that can store 3-5seconds worth of data at 100000 samples per second.
if you just want the peak, then still a precision shunt resistor and peak hold voltage on the fluke.
in-rush or surge current readings can be very high so size a shunt resistor as needed. clamps dampen out the spikes but can still give you a good idea, some fluke meters have an "in rush" button on them.

if you have a signal generator you put your fluke in the circuit and see how it responds to fast signals until the error gets outside your comfort zone.

The compressor will have a startup capacitors somewhere and that will affect the startup surge (in a good way hehe).
 
What kind of meter or sensor do I need to “see” an instantaneous amperage spike?
I would like to investigate the possibility of running the home heat pump.
View attachment 40022
I added a “Hard Start kit” when the 21KW Diesel genset demonstrated difficulty starting the compressor.
Now the genset does not sag when starting the compressor, but I have no idea what the modified LRA value is, so want to measure it.
I have a Fluke 177, w/ i410 AC/DC Current Clamp, but I am not sure it is fast enough.

I have room to install a second 6848 HW+ Pro.
If I understand how the two inverters will operate when stacked, 24kw of 30 second overload might be possible, enough to get the compressor started. That would be excellent!
This works fine for me:

 
@pvdude Here is a pic of 120v 10a 12000 btu window unit from Emporia view ac house monitor - 2nd pic of 240v 6.2 amp 19.5 seer Inverter mini-split 12000 btu ac, both powered off Growatt 6000t: 15 amp spike on one leg of Split phase Growatt - yuk
1627060843008.png1627060775926.png
 

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This works fine for me:


Yes, this one seems to correctly capture the peak current.

The Fluke 177 does not have a peak capture, you need to go up one model to get that function:

 
This is the one I routinely use. I have a much more expensive Fluke that can also read "inrush" and they are accurate to each other to within <1%.
 
This is the one I routinely use. I have a much more expensive Fluke that can also read "inrush" and they are accurate to each other to within <1%.
Yes, the Kaiweets is likely made by Uni-T, I see a lot of their stuff is just rebranded products. Certainly looks the same except for the brand name.
 
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